The present invention relates to a new and improved means and method for accurately transferring fuze timing data from a muzzle extension to a fast moving projectile which contains a programmable projectile fuze. The programmable projectile fuze comprises a fuze and a programmable counter, which is set to trigger the fuze, thereby exploding the projectile at the appropriate time. There is also provided an apparatus attached to the muzzle extension for measuring the muzzle velocity of the projectile in order to set or adjust the counter for triggering the fuze as a function of the muzzle velocity. A transmitter coil secured to the muzzle of the weapon inductively sets the counter.
In order to be able to set the programmable fuze with the requisite accuracy, 20 bits must be transmitted from the transmitter coil to the receiver coil. Assuming a projectile velocity of 900 fps or 0.0108 in/microseconds, there is a very short amount of time to transmit the muzzle velocity from the transmitter mounted in the muzzle of the weapon to the receiver on the projectile. Therefore, high frequencies are used to transmit the data.
In the prior art, two methods have generally been used to convey fuze set time. Previous inductive fuze transfer methods have used an analog voltage to convey fuze set time or a series of comma free base band pulses. Using an analog voltage has not been accurate enough or robust enough for most real applications. Similarly, transmitting comma free base band pulses requires a relatively large minimum inductance to insure that the data pulse is transferred. Furthermore, a substantial dead time between bits is needed to ensure that inductive storage from a previous bit dies down sufficiently before the next bit starts. Therefore, no previously known prior art involving inductive fuze transfer provides for carrier modulated pulses, error detection/correction and/or automatic projectile timing oscillator correction like the present invention does.